[thaumasiotes]

The reason is simple. Swamps are commercially strategic, since they're located on rivers.

For most of history, shipping goods over land didn't make much sense.

[pacaro]

This makes perfect sense, I guess they are swamps because that's the combination of rivers and flat ground

[thriftwy]

We would have Berlin on Rhine and Moscow on Volga river then. Much better climate and much busier rivers commercially.

For some reason, capitals tend to be on undesirable rivers.

[Piskvorrr]

...if this was the only condition for "what city becomes a capital." Looking at Germany, there's Hamburg, Köln, München...all on nice rivers, but none of them were the capital of Prussia when Germany was first unified - since Prussia was the essential driver of that political process, Berlin became the capital. Something of a coincidence in the grand scheme of things, really.

[thriftwy]

For some reason, it's usually a faraway landlocked province that triggers unification. Not the rich and coastal ones.

Turin-Savoy in Italy, Prussia in Germany.